1. Field of the Invention
This invention relates generally to the field of bus communication using time division multiplexing (TDM) and more particularly to a bus controller for a high speed time division multiplexed bus.
2. Background of the Invention
The present invention is intended to optimize versatility and speed in communications over a high speed time division multiplexed bus. This bus is used to transfer information from one device such as a modem or the like to another such as a digital service unit. In order to make such data transfers, the TDM bus is partitioned into frames of time slots which each carry a data word. The TDM bus controller of the present invention has the job of controlling access to and from the TDM bus.
Typically, the information is being transmitted between the TDM bus and a processor of some type. The processor handles communication with other devices such a modem, DTE (Data Terminal Equipment), etc. The TDM bus controller is responsible for making sure that the data destined for a particular address actually gets there when receiving information from the TDM bus. When transmitting information over the TDM bus, the TDM bus controller's job is to assure that the information is placed in the correct frame and time slot so that a proper communication link is established. When receiving information from the bus, the TDM bus controller's job is to assure that the correct information is being removed from the bus.
In general, the TDM bus is a high speed bus which is capable of operation at speeds many times faster than the processor with which it is communicating. Thus, the TDM bus controller has to be able to rapidly effect the proper transfer in an efficient manner. It is also desirable to assure that bursts of data are received in the proper order at the destination and to assure that all data channels are ultimately serviced. The present invention serves this function using an unique bus protocol and an unique internal token used to point to the storage location for a particular data word.